Authors' objectives: Many people infected with the Mycobacterium tuberculosis complex (the bacteria that cause tuberculosis [TB]) have an inactive stage of infection known as latent tuberculosis infection (LTBI). A person with LTBI is at risk of developing active TB. Screening for, and treating people with, LTBI is an important part of preventing adverse health outcomes, reducing the risk of reactivation and the further spread of tuberculosis in a community. We conducted a health technology assessment of interferon-gamma release assay (IGRA) for the detection of LTBI, compared to the standard tuberculin skin test (TST) to evaluate the diagnostic accuracy, cost-effectiveness, the budget impact of publicly funding, and health care provider preferences and values.

Authors' results and conclusions: Interferon-gamma release assay testing was found to have good diagnostic accuracy and to be cost-effective or cost-saving for LTBI in populations aligned with the recommended uses of the Standards. We estimate that publicly funding IGRA in Ontario for all examined population subgroups would result in additional costs of between $2.99 million and $18.80 million over 5 years, depending on how the test is used. In the population-specific analyses, we estimate a cost savings of $1.63 million or higher with IGRA testing in eligible BCG-vaccinated immigrant populations or BCG-vaccinated people identified via contact investigations. There was a preference for IGRA among health care practitioners, particularly to support people who may have challenges with the available alternative tests (e.g., TST).

Authors' recommendations: Ontario Health, based on guidance from the Ontario Health Technology Advisory Committee, recommends publicly funding interferon-gamma release assay (IGRA) testing for latent tuberculosis infection.

Authors' methods: We performed a systematic literature search of the clinical evidence as an overview of systematic reviews. We reported the findings of the identified reviews, including their quality assessment of the body of evidence. We performed a systematic literature search of the economic evidence and included published Canadian cost-effectiveness studies. We assessed the quality of the body of evidence according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) Working Group criteria. We developed a probabilistic decision-tree model to estimate the incremental costs of IGRA strategies versus TST alone over 1 year in eligible population subgroups. IGRA was examined as a single test and in a sequential pathway with tuberculin skin test (TST; the test order depended on the type of population). We considered subpopulations at high risk of LTBI for whom IGRA would be preferred, as indicated by the Canadian TB Standards published in 2022 (hereinafter, the Standards); e.g., people who received a Bacille Calmette-Guérin (BCG) vaccine, such as BCG-vaccinated immigrants and people identified in contact investigations. We also considered people with comorbid conditions or who were undergoing treatments that may cause low immune function and, hence, may test incorrectly negative. We estimated the total 5-year budget impact (in 2024 CAD) for publicly funding IGRA testing in Ontario. To contextualize the potential value of IGRA, we spoke with health care providers about people requiring TB testing for LTBI. We attempted to reach out to people who had experience with IGRA or TST but did not receive any feedback.

Project Status: Completed

URL for protocol: https://www.crd.york.ac.uk/PROSPERO/view/CRD42024504025

Year Published: 2024

URL for published report: https://www.hqontario.ca/evidence-to-improve-care/health-technology-assessment/reviews-and-recommendations/interferon-gamma-release-assay-testing-for-latent-tuberculosis-infection

English language abstract: An English language summary is available

Publication Type: Full HTA

Country: Canada

Organisation Name: Ontario Health

Contact Address: 525 University Ave, Toronto, ON M5G 2L3

Contact Name: Nancy Sikich, Director Health Technology Assessment

Contact Email: oh-hqo_hta@ontariohealth.ca

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